The document discusses the challenges and differences between Swift and Objective-C, highlighting the complexities of bridging the two languages. It emphasizes the importance of protocols, generics, and proper type handling in Swift while cautioning against using inheritance where protocols should be employed instead. Additionally, it provides examples of code to illustrate concepts like generic classes and protocol composition.

1. Protocols and the
Promised Land
@MicheleTitolo

2. Swift is shiny! And new!

3. Swift is not Objective-C

4. Interop

5. as? as? as?

6. as? lies

7. 🚫
let vendor = ObjcObject()
let items = vendor.giveMeItems() as? [Fruit]

8. let vendor = ObjcObject()
let items = vendor.giveMeItems().map { $0 as Fruit }

9. @objc spreads like a virus

10. 🚫
@objc protocol SomeProtocol {
func someFunc()
}
class MyClass: SomeProtocol {}

11. @objc protocol SomeProtocol {
func someFunc()
}
@objc class MyClass: NSObject, SomeProtocol {}

12. Swift > Objc > Swift

13. Can’t #import “MyApp-Swift.h” in
header

14. Can’t conform, can’t subclass

15. Bridging

16. many parts of Swift don’t bridge

17. Does this really need to be used in
Objective-C?

18. framework headers can’t be in
bridging header

19. use @import

20. Partial bridging

21. -Swift.h will leave out funcs/vars that
don’t bridge

22. Again: does this really need to be
bridged?

23. Type System

24. properties can have 1 type

25. protocol Themeable {}
class ListViewController: UIViewController, Themeable {}
var themedViewController: // UIViewController, Themeable ????

26. two workarounds

27. public protocol ViewControllerProtocol {
var view: UIView! { get }
var storyboard: UIStoryboard? { get }
init(nibName nibNameOrNil: String?, bundle nibBundleOrNil:
NSBundle?)
func viewDidLoad()
// etc
}
protocol ThemeableViewController: Themeable, ViewControllerProtocol {}
var themedViewController: ThemeableViewController
Swift-y but hack-y

28. var themed: Themeable {
get {
return self.viewController as! Themeable
}
set(newThemeable) {
if let themedViewController = newThemeable as? UIViewController{
viewController = themedViewController
}
}
}
var viewController: UIViewController
init<T where T: Themeable, T: UIViewController>(viewController: T) {
self.viewController = viewController
}
Also swfit-y also hack-y

29. Can’t override type with
inheritance

30. 🚫Deep object hierarchies

31. Protocols

32. Composition instead
of inheritance

33. Protocols and inheritance
don’t mix

34. use POP to mock

35. Generics

36. Can’t reference a generic protocol

37. protocol Holder {
typealias Item
var items: [Item] { get }
}
class Basket<Thing>: Holder{
var items: [Thing] = []
func add(item: Thing) {
items.append(item)
}
}

38. 🚫
🚫
var someHolder: Holder
var someBasket: Basket

39. 🚫 var someHolder: Holder<Peach>
var someBasket: Basket<Peach>

40. Covariance only works with generic
classes

41. Covariance: If a Cat is an Animal
func feed(animal: Animal)
can receive a Cat

42. 🚫
🚫
typealias Object
typealias Object: String
typealias RoundObject: Object

43. generic classes can specify type
requirements

44. class Basket<Thing: Fruit> {
var items: [Thing] = []
func add(item: Thing) {
items.append(item)
}
}

45. 🚫
class Basket<Thing: Fruit> {
var items: [Thing] = []
func add(item: Thing) {
items.append(item)
}
}
class FruitBasket: Basket<Fruit> {}
class PeachBasket: FruitBasket<Peach> {}

46. 🚫
class Bag<Stuff> {
class Basket<Thing: Stuff> {
var items: [Thing] = []
func add(item: Thing) {
items.append(item)
}
}
}

47. Generic non-NSObjects have
issues

48. Explicitly call out class for now

49. Swift introduces
awesome new patterns

50. Thanks!
@MicheleTitolo

51. Photo Credits
• https://www.flickr.com/photos/83073191@N00/21709516808/
• https://www.flickr.com/photos/64181484@N04/21946459678/
• https://www.flickr.com/photos/66904032@N05/18905223864/
• https://www.flickr.com/photos/27454212@N00/22120629112/
• https://www.flickr.com/photos/8725928@N02/24439195435/
• https://www.flickr.com/photos/28480761@N04/24143685631/